Lightweight Arm Research Articles

Computer-Monitored, 16-Channel Flight Mill for Recording the Flight of Leafhoppers (Homoptera: Auchenorrhyncha)

A multichannel, computer-monitored flight mill suitable for studying flight performance of small, weakly flying insects such as leafhoppers was developed. The flight mill uses a magnetic bearing and light-weight arm to minimize friction and drag. Sixteen mills can be monitored simultaneously by a PC. The construction of the mills and monitor, and data from a small number of test experiments, are presented. The problems associated with interpreting flight mill data are also considered.

Contact control for advanced applications of light weight arms

Many applications of robotic and teleoperated manipulator arms require operation in contact and noncontact regimes. This paper deals with both regimes and the transition between them with special attention given to problems of flexibility in the links and drives. This is referred to as contact control. Inverse dynamics is used to plan the tip motion of the flexible link so that the free motion can stop very near the contact surface without collision due to overshoot. Contact must occur at a very low speed since the high frequency impact forces are too sudden to be affected by any feedback generated torques applied to a joint at the other end of the link. The effects of approach velocity and surface properties are discussed. Force tracking is implemented by commands to the deflection states of the link and the contact force. This enables a natural transition between tip position and tip force control that is not possible when the arm is treated as rigid. The effects of feedback gain, force trajectory, and desired final force level are of particular interest and are studied. Experimental results are presented on a one-link arm and the system performance in the overall contact task is analyzed. Extension to multi-link cases with potential applications are discussed.

Lightweight Arm Boards

Lightweight Arm Boards

An experimental investigation of an articulating robotic manipulator with a graphite‐epoxy composite arm

AbstractAn experimental program was undertaken to investigate the elastodynamic response characteristics of a General Electric P50 robot retrofitted with a prototype graphite‐epoxy forearm. The retrofitted robot with this high‐strength, high‐stiffness lightweight arm was then programmed to execute a variety of maneuvers and the attendant elastodynamic deflections were measured. These experimental data were then compared with the results of complementary studies of the original robot which featured an aluminum arm. The preliminary experimental results from this proof‐of‐concept study clearly demonstrate the superior performance characteristics of the robot retrofitted with the composite arm.

A Methodology for Synthesizing High-Performance Robots Fabricated With Optimally Tailored Composite Laminates

An essential ingredient of the next generation of robotic manipulators will be high-strength lightweight arms which promise high-performance characteristics. Currently, a design methodology for optimally synthesizing these essential robotic components does not exist. Herein, an approach is developed for addressing this void in the technology-base by integrating state-of-the-art techniques in both the science of composite materials and also the science of flexible robotic systems. This approach is based on the proposition that optimal performance can be achieved by fabricating robot arms with optimal cross-sectional geometries fabricated with optimally tailored composite laminates. A methodology is developed herein which synthesizes the manufacturing specification for laminates which are specifically tailored for robotic applications in which both high-strength, high-stiffness robot arms are required which also possess high material damping. The parameters in the manufacturing specification include the fiber-volume fraction, the matrix properties, the fiber properties, the ply layups, the stacking sequence and the ply thicknesses. This capability is then integrated within a finite-element methodology for analyzing the dynamic response of flexible robots. An illustrative example demonstrates the approach by simulating the three-dimensional elastodynamic response of a robot subjected to a prescribed spatial maneuver.

Analysis and Design of a Direct-Drive Arm With a Five-Bar-Link Parallel Drive Mechanism

The direct-drive arm that has no gears between motors and their loads have several important advantages including no backlash, small friction, and high mechanical stiffness. The arm mechanism, however, becomes extremely massive, when each motor is directly attached to its joint along a serial linkage mechanism. The complicated dynamics resulting from varying inertia, interactions, and nonlinearities, is also more prominent than that of a robot with gears. This paper describes a lightweight arm mechanism with invariant and decoupled inertia characteristics. Instead of having motors at serial joints, a parallel drive mechanism with a closed-loop five bar linkage is utilized. The dynamic behavior of this mechanism is analyzed and the condition for the elimination of the interactions and nonlinearities in the mass properties is derived. The decoupled and invariant arm dynamics significantly reduces the complexity of controlling the direct-drive arm. In the latter half of the paper, a prototype robot developed on this basis is described. By using high torque brushless motors which were specially designed for the direct-drive robot, top speed and maximum acceleration were increased by an order-of-magnitude to about 10 m/s and 5 G, respectively.